1. Field of the Invention
This invention relates to fluidic lenses and in particular, but not exclusively, lenses for use with light of wavelength in the visible, near infra-red (IR) and in the range 3-5 μm.
2. Description of Related Art
The term “light” as used herein includes infra-red and ultraviolet as well as visible light.
A variable-focus fluidic lens has been described for example in “Variable-focus liquid lens”, H. Ren et al, Optics Express Vol. 15, No. 10, 5931-5936, 14 May 2007. The fluidic lens in that case is based upon a pressure-induced liquid redistribution within a lens cell. In this case the liquid used is pure water, but other fluids could be used. However, because of the influence of gravity, there is a tendency for such lenses to sag if their aperture is increased above a few millimetres. In addition, the simple structure of the lens makes it impossible for it to be achromatic in nature (i.e. able to focus parallel rays of different wavelengths to the same point).